Methods and apparatus for volume adjustment

ABSTRACT

Apparatus, systems, articles of manufacture, and methods for volume adjustment are disclosed herein. An example method includes identifying media represented in an audio signal, accessing metadata associated with the media in response to identify the media in the audio signal, determining, based on the metadata, an average volume for the media, and adjusting an output volume of the audio signal based on an average gain value, the average gain value determined based on the average volume for the media.

RELATED APPLICATION(S)

This patent claims the benefit of and priority to U.S. ProvisionalApplication Ser. No. 62/614,439, entitled “METHODS AND APPARATUS FORDYNAMIC VOLUME ADJUSTMENT,” filed on Jan. 7, 2018. U.S. ProvisionalApplication Ser. No. 62/614,439 is hereby incorporated by reference inits entirety.

FIELD OF THE DISCLOSURE

This disclosure relates generally to volume adjustment, and, moreparticularly, to methods and apparatus for volume adjustment.

BACKGROUND

In recent years, a multitude of media of varying characteristics hasbeen delivered using an increasing number of channels. Audio media,specifically, may be received using more traditional channels (e.g., theradio), or using more recently developed channels, such as usingInternet-connected streaming devices. As these channels have developed,systems which are able to process and output audio from multiple sourceshave been developed as well. Some automobile media systems, for example,are capable of delivering media from compact discs (CD's), Bluetoothconnecting devices, universal serial bus (USB) connected devices,connected devices, auxiliary inputs, and other sources.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic illustration of an example system constructed inaccordance with the teachings of this disclosure for volume adjustment.

FIG. 2 a block diagram showing additional detail of the media unit ofFIG. 1.

FIG. 3 is a flowchart representative of example machine readableinstruction that may be used to implement the media unit 106 of FIGS. 1and 2 to perform volume adjustment.

FIG. 4 is a flowchart representative of example machine readableinstructions that may be used to implement the media unit 106 of FIGS. 1and 2 to output the audio signal and provide real time volume adjustmentof the audio signal.

FIG. 5 is a flowchart representative of example machine readableinstructions that may be used to implement the media unit 106 of FIGS. 1and 2 to perform volume adjustment to normalize volume between sourcesand between media.

FIG. 6 is a schematic illustration of an example processor platform thatmay execute the instructions of FIGS. 3-5 to implement the example mediaunit 106 of FIGS. 1 and 2.

The figures are not to scale. Wherever possible, the same referencenumbers will be used throughout the drawing(s) and accompanying writtendescription to refer to the same or like parts.

DETAILED DESCRIPTION

In conventional audio media implementations, audio signals associatedwith different media may have different volumes. For example, media onone CD may be recorded and/or mastered at a significantly differentvolume than media of another CD. Similarly, media retrieved from astreaming device may have significantly different volume levels thanmedia retrieved from a different device, or media retrieved from thesame device via a different application. As users increasingly listen tomedia from a variety of different sources, differences in volume levelsbetween sources and between media of the same source can become verynoticeable, and potentially irritating to a listener.

In some conventional approaches to volume regularization, dynamic rangecompressors are utilized to compress the overall dynamic range of anaudio signal to satisfy a volume threshold. In some conventionalimplementations, such dynamic range compression continually monitors andadjusts the volume of the audio signal in order to satisfy a volumethreshold for the audio signal. Such continuous adjustment has an impacton a listener's perception of the audio signal, as the original dynamicsof the track are significantly altered. In some examples, dynamic rangecompression significantly degrades the perceived quality of the audiosignal.

In example methods, apparatus, systems and articles of manufacturedisclosed herein, media metadata is used to determine an average audiolevel for a unit of media (e.g., a song, track, etc.). The average audiolevel is then utilized to determine an appropriate gain value to applyto the audio signal to achieve a desired volume level (also referred toherein as a target volume level). In some examples, the desired volumelevel is maintained throughout all audio signals such that all signalsare output at a consistent average volume level to enable an optimaluser experience. Further, in some examples, the volume level ismonitored at regular increments during output of the audio signal todetermine whether the volume level of the segments has an average volumethat satisfies the volume threshold. In such examples, the volume canagain be dynamically adjusted to account for differences between thevolume during the segment and the desired volume level. Further, formedia that has been altered or adjusted such that the volume levels areno longer the same as the volume levels represented in the media, themonitoring at regular increments will prevent the incorrect gain basedon the metadata from adjusting the volume of the audio signal to beoutside the desired range.

In example methods, apparatus, systems and articles of manufacturedisclosed herein, volume levels may be adjusted to ensure the volumeremains within a safe listening volume range. For example, if arelatively quiet track is amplified, and then playback transitions to atrack which already has very high volume, the volume level would need tobe adjusted to avoid playing the new track at a dangerous volume level(e.g., a volume level which may damage human hearing or renderingequipment quickly). In some examples disclosed herein, a buffer (e.g., aone-second buffer, a three-second buffer, etc.) is employed to act as adelay between the time the audio signal is input from a source (e.g., adisc, a radio station, a mobile phone, etc.) and the time it is output,thereby preventing rapid fluctuations in volume levels, and enablinganalysis and adjustment of volume levels during the buffer period.

In some example techniques disclosed herein, audio watermarks areutilized to identify media in order to retrieve metadata pertaining tothe audio signal. Audio watermarking is a technique used to identifymedia such as television broadcasts, radio broadcasts, advertisements(television and/or radio), downloaded media, streaming media,prepackaged media, etc. Existing audio watermarking techniques identifymedia by embedding one or more audio codes (e.g., one or morewatermarks), such as media identifying information and/or an identifierthat may be mapped to media identifying information, into an audioand/or video component. In some examples, the audio or video componentis selected to have a signal characteristic sufficient to hide thewatermark. As used herein, the terms “code,” or “watermark” are usedinterchangeably and are defined to mean any identification information(e.g., an identifier) that may be inserted or embedded in the audio orvideo of media (e.g., a program or advertisement) for the purpose ofidentifying the media or for another purpose such as tuning (e.g., apacket identifying header). As used herein “media” refers to audioand/or visual (still or moving) content and/or advertisements. Toidentify fingerprinted media, the watermark(s) are extracted and used toaccess a table of reference watermarks that are mapped to mediaidentifying information.

In some example techniques disclosed herein, audio fingerprints areutilized to identify media in order to retrieve metadata pertaining tothe audio signal. Audio fingerprinting is a technique used to identifymedia such as television broadcasts, radio broadcasts, advertisements(television and/or radio), downloaded media, streaming media,prepackaged media, etc. Unlike media monitoring techniques based oncodes and/or watermarks included with and/or embedded in the monitoredmedia, fingerprint or signature-based media monitoring techniquesgenerally use one or more inherent characteristics of the monitoredmedia during a monitoring time interval to generate a substantiallyunique proxy for the media. Such a proxy is referred to as a signatureor fingerprint, and can take any form (e.g., a series of digital values,a waveform, etc.) representative of any aspect(s) of the media signal(s)(e.g., the audio and/or video signals forming the media presentationbeing monitored). A signature may be a series of signatures collected inseries over a timer interval. A good signature is repeatable whenprocessing the same media presentation, but is unique relative to other(e.g., different) presentations of other (e.g., different) media.Accordingly, the term “fingerprint” and “signature” are usedinterchangeably herein and are defined herein to mean a proxy foridentifying media that is generated from one or more inherentcharacteristics of the media.

Signature-based media monitoring generally involves determining (e.g.,generating and/or collecting) signature(s) representative of a mediasignal (e.g., an audio signal and/or a video signal) output by amonitored media device and comparing the monitored signature(s) to oneor more references signatures corresponding to known (e.g., reference)media sources. Various comparison criteria, such as a cross-correlationvalue, a Hamming distance, etc., can be evaluated to determine whether amonitored signature matches a particular reference signature. When amatch between the monitored signature and one of the referencesignatures is found, the monitored media can be identified ascorresponding to the particular reference media represented by thereference signature that with matched the monitored signature. Becauseattributes, such as an identifier of the media, a presentation time, abroadcast channel, etc., are collected for the reference signature,these attributes may then be associated with the monitored media whosemonitored signature matched the reference signature.

In some example techniques disclosed herein, audio signals areidentified by text matching (e.g., utilizing text pertaining to anartist, album, title, etc.) or using identifiers associated with theaudio signal (e.g., a catalog identifier embedded in an ID3 tag, an ISRCidentifier, etc.). Example techniques disclosed herein may utilize anyaudio signal identification technique to identify audio signals.

In some example techniques disclosed herein, audio signals that are notidentifiable, and hence audio signals for which metadata is notavailable, are dynamically compressed so as to maintain the desiredvolume level. For example, a commercial may play in between identifiableaudio signals pertaining to media with metadata. In such an example, thevolume level would be adjusted based on the average volume level foreach of the identifiable audio signals and dynamic compression would beused to adjust the volume level of the commercial in between, to avoid adrastic shift in volume.

In examples disclosed herein, volume adjustment may be performed by acomponent of, or by a component in communication with, an audio systemof a vehicle. In some examples, a media unit including a dynamic volumeadjuster or other component capability of dynamic volume adjustment maybe included in the vehicle's head unit. In such examples, the vehiclehead unit may receive audio signals from an auxiliary input, a CD input,a radio signal receiver input, an external stream from a smart device, aBluetooth input, a network connection (e.g., a connection to theInternet), or via any other source. For example, the dynamic volumeadjustment may be performed on a media system in a home entertainmentsystem, wherein multiple sources (e.g., a DVD player, a set top box,etc.) may communicate audio signals that are dynamically adjusted toattempt to normalize volume levels between sources and media. In otherexamples, dynamic volume adjustment may be performed in any setting orfor any media device(s).

In example methods, apparatus, systems and articles of manufacturedisclosed herein, a volume setting specified by a user is stored inassociation with data identifying a source type. For example, a volumelevel selected by a user while operating their mobile device may bestored. Additionally or alternatively, the volume level may beautomatically adjusted utilizing techniques disclosed herein to satisfya user preference or a safety requirement when a specific input sourceis in use. Some such volume levels can be leveraged when a source changeoccurs to configure an initial volume level. For example, if the userswitches an audio source from a radio to the mobile device, exampletechniques disclosed herein reference a historical audio setting for themobile device to configure an initial volume level. Similarly,historical volume settings can be used to compare current volume levelsfor an input source with historical levels and make adjustments toensure a consistent and safe listener experience.

FIG. 1 is a schematic illustration of an example system 100 constructedin accordance with the teachings of this disclosure for volumeadjustment. The example system 100 includes media devices 102, 104 thattransmit audio signals to a media unit 106. The media unit 106 processesthe audio signals and transmits the signals to an audio amplifier 108,which subsequently outputs the amplified audio signal to be presentedvia an output device 110.

The example media device 102 of the illustrated example of FIG. 1 is aportable media player (e.g., an MP3 player). The example media device102 stores or receives audio signals corresponding to media and iscapable of transmitting the audio signals to other devices. In theillustrated example of FIG. 1, the media device 102 transmits audiosignals to the media unit 106 via an auxiliary cable. In some examples,the media device 102 may transmit audio signals to the media unit 106via any other interface.

The example media device 104 of the illustrated example of FIG. 1 is amobile device (e.g., a cell phone). The example media device 104 storesor receives audio signals corresponding to media and is capable oftransmitting the audio signals to other devices. In the illustratedexample of FIG. 1, the media device 104 transmits audio signals to themedia unit 106 wirelessly. In some examples, the media device 104 mayuse Wi-Fi, Bluetooth, and/or any other technology to transmit audiosignals to the media unit 106. In some examples, the media device 104may interact with components of a vehicle or other devices for alistener to select media for presentation in the vehicle. The mediadevices 102, 104 may be any devices which are capable of storing and/oraccessing audio signals. In some examples, the media devices 102, 104may be integral to the vehicle (e.g., a CD player, a radio, etc.).

The example media unit 106 of the illustrated example of FIG. 1 iscapable of receiving audio signals and processing them. In theillustrated example of FIG. 1, the example media unit 106 receives mediasignals from the media devices 102, 104 and processes them to performvolume adjustment. The example media unit 106 is capable of identifyingaudio signals based on identifiers embedded in or derived from the media(e.g., fingerprints, watermarks, signatures, etc.). The example mediaunit 106 is additionally capable of accessing metadata corresponding tomedia associated with an audio signal. In some examples, the metadata isstored in a storage device of the media unit 106. In some examples, themetadata is accessed from another location (e.g., from a server via anetwork). Further, the example media unit 106 is capable of performingdynamic volume adjustment by determining and applying average gainvalues based on the metadata to adjust the average volume of an audiosignal to satisfy a volume threshold. The example media unit 106 isadditionally capable of monitoring audio that is being output by theoutput device 110 to determine the average volume level of audiosegments in real time. In the event that an audio signal is notidentified as corresponding to media, and/or in the event that metadataincluding volume information is not available for an audio signal, theexample media unit 106 is capable of dynamic range compression toprovide compression of the audio signal to achieve a desired volumelevel. In some examples, the example media unit 106 is included as partof another device in a vehicle (e.g., a car radio head unit). In someexamples, the example media unit 106 is implemented as software and isincluded as part of another device, available either through a directconnection (e.g., a wired connection) or through a network (e.g.,available on the cloud). In some examples, the example media unit 106may be incorporated with the audio amplifier 108 and the output device110 and may output audio signals itself following processing of theaudio signals.

The example audio amplifier 108 of the illustrated example of FIG. 1 isa device that is capable of receiving the audio signal that has beenprocessed by the media unit 106 and performing the appropriateamplification of the signal for output by the output device 110. In someexamples, the audio amplifier 108 may be incorporated into the outputdevice 110. In some examples, the audio amplifier 108 amplifies theaudio signal based on an amplification output value from the media unit106. In some examples, the audio amplifier 108 amplifies the audiosignal based on an input from a listener (e.g., a passenger or driver ina vehicle adjusting a volume selector).

The example audio output device 110 of the illustrated example of FIG. 1is a speaker. In some examples, the audio output device 110 may bemultiple speakers, headphones, or any other device capable of presentingaudio signals to a listener. In some examples, the output device 110 maybe capable of outputting visual elements (e.g., video) as well (e.g., atelevision with speakers). In some such examples, the visual elementsmay be utilized to identify media (e.g., based on a watermark includedin the video, based on a fingerprint derived from the video, etc.). Insome such examples, in addition to or alternatively to volumeadjustment, techniques described herein may be implemented to adjustcharacteristics of the video (e.g., adjust a luminance, perform gammacorrection, perform color balance correction, etc.) based onidentification of the media represented in the video.

While the illustrated example system 100 of FIG. 1 is described inreference to a volume adjustment implementation in a vehicle, some orall of the devices included in the example system 100 may be implementedin any environment, and in any combination. For example, the system 100may be in an entertainment room of a house, wherein the media devices102, 104 may be gaming consoles, virtual reality devices, set top boxes,or any other devices capable of accessing and/or transmitting media.Additionally, in some examples, the media may include visual elements aswell (e.g., television shows, films, etc.).

A block diagram 200 providing additional detail of an exampleimplementation of the media unit 106 is illustrated in FIG. 2. Theexample media unit 106 is capable of receiving an audio signal andprocessing the audio signal to dynamically adjust the volume of theaudio signal to a desired level. Following the dynamic volumeadjustment, the example media unit 106 transmits the audio signal to theaudio amplifier 108 for amplification prior to output by the outputdevice 110.

As shown in FIG. 2, the illustrated example media unit 106 contains adynamic volume adjuster 202, a data store 204, a metadata database 206,and a dynamic range compressor 208. The dynamic volume adjuster 202further includes an audio signal accessor 210, an audio signalidentifier 212, a metadata accessor 214, a volume adjuster 216, a realtime audio monitor 218, and an audio signal outputter 220.

The example dynamic volume adjuster 202 is capable of receiving an audiosignal and performing dynamic volume adjustment on the audio signal. Insome examples, the example dynamic volume adjuster 202 identifies audiosignals that are accessed by the dynamic volume adjuster 202. In someexamples, the dynamic volume adjuster 202 may access the audio signalsfrom the data store 204 where the signals may be temporarily storedduring processing. In some examples, the dynamic volume adjuster 202utilizes identifiers embedded in the audio signal to determine the mediacorresponding to the audio signal. The example dynamic volume adjuster202 may use any technique to determine the media that corresponds to thereceived audio signal. In some examples, the volume adjuster 202 iscapable of obtaining metadata corresponding to volume information (e.g.,average volume across a unit of media, average volume during a segmentof media, etc.). In some examples, the example volume adjuster 202 iscapable of determining an appropriate average gain value to apply to anaudio signal to achieve a desired average volume for the audio signal.In some examples, the example volume adjuster 202 presents (e.g.,outputs) the audio signal to the audio amplifier 108 of the illustratedexample of FIG. 1 in samples and continually collects real time volumemeasurements on the samples as the audio sample is presented. In suchexamples, the example volume adjuster 202 generates an average volumelevel for segments of the audio signal (e.g., three second segments) anddetermines if the average volume level for the segment satisfies avolume threshold. In some examples, the example volume adjuster 202 ispreconfigured with a desired volume level and a volume threshold. Theexample volume adjuster 202 may, in response to a segment not having anaverage volume level satisfying the threshold, adjust the gain of theoverall audio signal to be presented. In some examples, the examplevolume adjuster 202 may utilize metadata corresponding to average volumelevels for segments throughout the audio sample (e.g., running volumeestimate data) to determine one or more gain values that may beimplemented at one or more different segments of the audio signal. Insome examples, the volume adjuster 202 may continually monitor mediaidentifiers (e.g., fingerprints) pertaining to media in the audio signalto determine if a change in media being transmitted has occurred.

The example data store 204 of the illustrated example of FIG. 2 is astorage location for audio signals and other data utilized by the mediaunit 106. The data store 204 may be implemented by a volatile memory(e.g., a Synchronous Dynamic Random Access Memory (SDRAM), DynamicRandom Access Memory (DRAM), RAMBUS Dynamic Random Access Memory(RDRAM), etc.) and/or a non-volatile memory (e.g., flash memory). Thedata store 204 may additionally or alternatively be implemented by oneor more double data rate (DDR) memories, such as DDR, DDR2, DDR3, mobileDDR (mDDR), etc. The data store 204 may additionally or alternatively beimplemented by one or more mass storage devices such as hard diskdrive(s), compact disk drive(s) digital versatile disk drive(s), etc.While in the illustrated example the data store 204 is illustrated as asingle database, the data store 204 may be implemented by any numberand/or type(s) of databases. Furthermore, the data stored in the datastore 660 may be in any data format such as, for example, binary data,comma delimited data, tab delimited data, structured query language(SQL) structures, etc. In some examples, the example data store 204 andthe example metadata database 206 may be the same storage location. Insome examples, the data store 204 may be a virtual storage location(e.g., a server accessible via a network).

The example metadata database 206 is a storage location for metadatacorresponding to media. The example metadata database 206 providesmetadata to the example metadata accessor 214 pertaining to media thathas been identified in the audio signal by the example audio signalidentifier 212. In some examples, the metadata stored in the metadatadatabase 206 includes information such as average volume information forunits of media (e.g., tracks, songs, etc.) and/or average volumeinformation for segments of units of media (e.g., three second intervalsthroughout a song). The example metadata database 206 may be implementedby a volatile memory (e.g., a Synchronous Dynamic Random Access Memory(SDRAM), Dynamic Random Access Memory (DRAM), RAMBUS Dynamic RandomAccess Memory (RDRAM), etc.) and/or a non-volatile memory (e.g., flashmemory). The metadata database 206 may additionally or alternatively beimplemented by one or more double data rate (DDR) memories, such as DDR,DDR2, DDR3, mobile DDR (mDDR), etc. The metadata database 206 mayadditionally or alternatively be implemented by one or more mass storagedevices such as hard disk drive(s), compact disk drive(s) digitalversatile disk drive(s), etc. While in the illustrated example themetadata database 206 is illustrated as a single database, the metadatadatabase 206 may be implemented by any number and/or type(s) ofdatabases. Furthermore, the data stored in the metadata database 206 maybe in any data format such as, for example, binary data, comma delimiteddata, tab delimited data, structured query language (SQL) structures,etc.

The example dynamic range compressor 208 of the illustrated example ofFIG. 2 is capable of compressing and/or expanding the dynamic range ofaudio signals that are not identified and/or audio signals for whichcorresponding metadata is not available to meet the desired volumerequirement. In some examples, the dynamic range compressor 208 performsaudio dynamic range compression and/or audio dynamic range expansionsuch that the signal has an average volume level that satisfies thevolume threshold related to the desired volume level. In some examples,the dynamic range compressor runs continuously in the background and itactivated whenever the volume adjuster 216 is unable to dynamicallyadjust the volume of the audio signal due to a lack of metadata, or alack of identifiable media. The example dynamic range compressor 208performs compression such that when the audio signal has a volumeamplitude that does not satisfy the volume threshold related to thedesired volume value, the signal is compressed or expandedinstantaneously. In such examples, the local dynamic range of the audiosignal may be altered due to the compression or expanded. In someexamples, the example dynamic range compressor 208 forwards the audiosignal, or a portion of the audio signal, to the real time audio monitor218 after the audio signal, or a portion of the audio signal, has beencompressed.

The example audio signal accessor 210 of the illustrated example of FIG.2 accesses audio signals for processing. In some examples, the exampleaudio signal accessor 210 receives signals from the media devices 102,104 of the illustrated example of FIG. 1. In some examples, the audiosignal accessor 210 retrieves audio signals from the data store 204,which may act as a temporary buffer for incoming audio signals prior toprocessing. In some examples, the audio signal accessor 210 implements abuffer (e.g., a one second buffer) which results in a delay between atime the audio signal is initially accessed and a time the audio signalis output, to provide the dynamic volume adjuster 202 with time foranalysis and volume adjustment. During the buffer period, the audiosignal can be identified by the audio signal identifier 212, metadatacan be retrieved for the audio signal by the metadata accessor 214,volume levels can be compared with reference audio levels (e.g. from themetadata, from a historical volume setting, etc.), volume levels ofportions of the audio signal can be adjusted, and/or volume levels ofthe entirety of the audio signal can be adjusted. Any analysis and/orvolume adjustment steps may occur during the buffer period to improvevolume consistency, user experience, and/or volume level safety. Theexample audio signal accessor 210 may receive audio signals from anysource, and of any format. The audio signal accessor 210 of theillustrated example communicates audio signals to the real time audiomonitor 218, the audio signal identifier 212, and/or any other componentof the media unit 106.

The example audio signal identifier 212 of the illustrated example ofFIG. 2 identifies media corresponding to the audio signal that isaccessed by the example audio signal accessor 210. In some examples, theaudio signal identifier 212 performs a comparison of a media identifier(e.g., a fingerprint) embedded in an audio signal with known orreference audio signatures to determine media of the audio signal. Inthe event that the example audio signal identifier 212 does not find asignature in the media to perform identification, the example audiosignal identifier 212 directs the dynamic range compressor 208 toperform dynamic compression of the audio signal. Similarly, in the eventthat the example audio signal identifier 212 finds a signature but isunable to determine the media based on a match with a reference, theexample audio signal identifier 212 directs the dynamic range compressor208 to perform dynamic compression of the audio signal. In someexamples, the example audio signal identifier 212 is able to find amatching reference signature. In such examples, the audio signalidentifier 212 may pass the identification information to the examplemetadata accessor 214 to access metadata corresponding to the media. Insome examples, the audio signal identifier 212 may interact with anexternal database (e.g., at a central facility) to find a matchingreference signature. In some examples, the audio signal identifier 212may interact with an internal database (e.g., the data store 204 and/orthe metadata database 206) to find a matching reference signature. Insome examples, the audio signal identifier 212 utilizes watermarks toidentify the audio signal. In some example, the audio signal identifier212 utilizes other identifies (e.g., a catalog identifier embedded in anID3 tag, an ISRC identifier, etc.) to identify the audio signal. Theaudio signal identifier 212 may utilize any technique to identify theaudio signal.

The example metadata accessor 214 of the illustrated example of FIG. 2is capable of accessing metadata corresponding to media identified bythe audio signal identifier 212. In some examples, the metadata accessor214 extracts information pertaining to an average volume of a unit ofmedia (e.g., a track) and running volume levels throughout the unit ofmedia (e.g., the track). In some examples, the metadata may be retrievedfrom the metadata database 206. In some examples, the metadata may beretrieved from an external location (e.g., a storage location at acentral facility, a storage location accessible via a network, etc.). Insome examples, the available metadata may be processed by the metadataaccessor 214 to provide usable data for the dynamic volume adjuster 202.In some examples, volume metrics may be processed using existingtechniques and standards (e.g., algorithms to measure audio programmerloudness as presented in ITU-R standard BS.1770-4, which is herebyincorporated by reference herein). For example, the metadata may includevolume information at every segment of time and the metadata accessor214 may determine an average volume for an entire span of time. In someexamples, the metadata accessor 214 may perform any calculations ortransformations necessary to arrive at useful data to perform dynamicvolume adjustment. In some examples, the metadata accessed by themetadata accessor 214 may include a value representing the differencebetween the average volume of the media and the desired volume, whichmay subsequently be used to apply an average gain to the audio signal.

The example volume adjuster 216 of the illustrated example of FIG. 2adjusts the volume level of an audio signal. In some examples, theexample volume adjuster 216 determines a single average gain value thatwill transform the volume of an audio signal from a known volume value(e.g., as indicated in the metadata) to a desired volume value (e.g., apreconfigured value). In such examples, the example volume adjuster 216applies the gain value to the entire audio signal to transform the audiosignal. In some examples, the example volume adjuster 216 mayadditionally or alternatively apply a gain value in real-time to anaudio signal that is being output in response to the output level (e.g.,volume level) that has been fed back from the real time audio monitor218 and the average volume level for a specified segment of the audiosignal (e.g., a sample or multiple samples) not satisfying the volumethreshold (e.g., satisfying a volume target) related to the desiredvolume level. In some examples, the example volume adjuster 216 mayapply a global gain value to the entire audio signal based on theaverage volume level indicated by the metadata for the media. In someexamples, the example volume adjuster 216 may apply a local gain valueto areas of the audio signal that have significantly different (e.g.,lower or higher) volumes than other segments of the audio signal, basedon large volume changes indicated in the metadata and/or based onreal-time data collected by the example real time audio monitor 218 thatindicates the threshold has not been satisfied (e.g., the target outputlevel has not been achieved). In some examples, the metadata retrievedby the metadata accessor 214 includes data indicating directly theappropriate gain to apply to the audio signal to achieve a desiredvolume level. In some examples, the example volume adjuster 216 may haveforward-looking adjustment capabilities by using a continuous volumestream included in the metadata accessed by the metadata accessor 214.In some examples, the example volume adjuster 216 may work in tandemwith the example real time audio monitor 218 and the metadata accessor214 to make adjustments to the volume to account for changes in thedynamic range of an audio signal before these changes occur. Forexample, the continuous volume stream included in the metadata accessedby the metadata accessor 214 may indicate a large volume change that thevolume adjuster 216 can correct for by applying a slow moving volumechange before the large volume event occurs. Thus, prior to the volumechange indicated in the metadata, the example volume adjuster 216 maygradually adjust the gain value to the audio signal and consequentlyadjust the volume of the media.

In addition, the real time audio monitor 218 may indicate that thevolume threshold is not satisfied (e.g., the target volume level is notachieved) and supply the volume adjuster 216 with an additionalcorrection factor to be applied in real time. In some examples, a slowand imperceptible shift in the dynamic range of the audio may resultfrom the application of the correction factor, in contrast to thecompression that is applied by the example dynamic range compressor 208.

In some examples, the volume adjuster 216 makes a single volumeadjustment at a time when new media is detected and/or when a new sourceis detected. Such an approach may be preferable in some examplescompared to continual volume adjustments, as a single volume adjustmentcan be made to normalize between sources and between media, and thenthis desired volume level can be maintained (thereby avoiding noticeablevolume adjustments) until a new source or new media is detected. In somesuch examples, the volume adjuster 216 computes a first gain based onthe average volume of the media as indicated in the metadata to enablenormalization between different media, and a second gain based on acomparison of the input audio signal and an instantaneous volumemeasurement represented in the metadata to enable normalization ofvolume between sources. The volume adjuster 216 utilizes an unalteredvolume of the input audio signal to determine the second gain value bycomparing this initial, unaltered volume with the instantaneous volumein the metadata from the metadata accessor 214. The volume adjuster 216then computes an applied gain value based on both the first and secondgain values, and adjusts the volume of the input audio signal based onthis applied gain value. In some such examples, the first and the secondgain values are both based on volume measurements before a gain value isapplied (e.g., based on the unaltered input audio signal).

In some examples, the volume adjuster 216 adjusts volume levels for onlyportions of the audio signal. For example, the volume adjuster 216 mayadjust a volume level for a specific channel (e.g., increasing volume inthe center channel in a 5.1 mix to improve perceptibility of dialog in amovie).

In some examples, the volume levels configured by the volume adjuster216 are stored as historical data. In some examples, historical volumelevels are utilized when a source changes (e.g., a transition from radioto auxiliary input, a transition from a CD to a radio input, etc.) toset an initial volume level. In some examples, the real time audiomonitor 218 compares current volume levels with historical volume levelsassociated with a source and/or with a user and causes the volumeadjuster 216 to adjust volume levels accordingly (e.g., reduce volumelevels to conform with a user's historical preference, reduce volumelevels to remain within a safe listening volume range, etc.).

The example real time audio monitor 218 of the illustrated example ofFIG. 2 collects real time volume measurement data, generates averagevolume levels for samples of the audio signal, and determines if asegment of the audio signal has an average volume value that does notsatisfy the volume threshold (e.g., the target volume) related to thedesired volume level. The example real time audio monitor 218 monitorsthe input audio signal accessed by the audio signal accessor 210 and theaudio output of the media unit 106 after audio signals have been alteredby the volume adjuster 216 and/or after audio signals have been alteredby the dynamic range compressor 208. In some examples, the real timeaudio monitor 218 may collect volume data directly from the processedaudio signals prior to the output of the processed audio signals. Insome examples, the real time audio monitor 218 may also collect volumedata from a separate measurement device or mechanism (e.g., the volumestream from the metadata accessed by the metadata accessor 214). Theexample real time audio monitor 218, in response to determining asegment of the audio signal does not satisfy the volume threshold (e.g.,the target volume) related to the desired volume level, may provide datato the volume adjuster 216. The example volume adjuster 216 may thensubsequently apply a gain value locally or globally (e.g., throughoutthe entire audio signal) to correct the audio signal such that the audiosignal then satisfies the volume threshold related to the desired volumelevel. In some examples, the example real time audio monitor 218 may bepreconfigured with a sample interval range within which the real timeaudio level is calculated (e.g., seven hundred fifty milliseconds tothree seconds). In some examples, the calculated output volume level iscompared with the stream of data from the metadata accessed by themetadata accessor 214 within a sampling range (e.g., seven hundred fiftymilliseconds to three seconds) to calculate the average volume level ofthe audio signal and the difference of this level from the target volumelevel. In some examples, the sample size, sample frequency, and otherparameters (e.g., thresholds) may be configurable.

In some examples where a gain value is calculated to normalize betweensources, the real time audio monitor 218 determines an initial volume ofthe unaltered input audio signal and communicates this volume to thevolume adjuster 216 for a gain value to be calculated. In some suchexamples, the real time audio monitor 218 may determine whether a sourcechange has occurred or a change in media has occurred, thereby enablingthe volume adjuster 216 to calculate a new gain value to normalizebetween different media and/or different sources.

In some examples, the real time audio monitor 218 compares currentvolume levels to a safe volume level range and/or a safe volumethreshold. For example, the real time audio monitor 218 can beconfigured to cause a volume reduction when volume levels exceed a safelistening volume threshold.

The example audio signal outputter 220 of the illustrated example ofFIG. 2 outputs the audio signal for presentation. In some examples, theaudio signal outputter 220 performs transformations on the audio signalto meet requirements of the output device 110 of FIG. 1. In someexamples, after an audio signal is compressed by the dynamic rangecompressor 208, it is transmitted to the audio signal outputter 220 ofthe dynamic volume adjuster 202. In some examples, the example audiosignal outputter 220 is in direct communication with the real time audiomonitor 218 to enable a final verification that the audio signal meetsthe volume requirements prior to transmitting the audio signal to anamplifier or output device.

While an example manner of implementing the media unit 106 of FIG. 1 isillustrated in FIG. 2, one or more of the elements, processes and/ordevices illustrated in FIG. 2 may be combined, divided, re-arranged,omitted, eliminated and/or implemented in any other way. Further, theexample dynamic volume adjuster 202, the example data store 204, theexample metadata database 206, the example dynamic range compressor 208,the example audio signal accessor 210, the example audio signalidentifier 212, the example metadata accessor 214, the example volumeadjuster 216, the example real time audio monitor 218, the example audiosignal outputter 220 and/or, more generally, the example media unit 106of FIG. 1 may be implemented by hardware, software, firmware and/or anycombination of hardware, software and/or firmware. Thus, for example,any of the example dynamic volume adjuster 202, the example data store204, the example metadata database 206, the example dynamic rangecompressor 208, the example audio signal accessor 210, the example audiosignal identifier 212, the example metadata accessor 214, the examplevolume adjuster 216, the example real time audio monitor 218, theexample audio signal outputter 220 and/or, more generally, the examplemedia unit 106 could be implemented by one or more analog or digitalcircuit(s), logic circuits, programmable processor(s), applicationspecific integrated circuit(s) (ASIC(s)), programmable logic device(s)(PLD(s)) and/or field programmable logic device(s) (FPLD(s)). Whenreading any of the apparatus or system claims of this patent to cover apurely software and/or firmware implementation, at least one of theexample dynamic volume adjuster 202, the example data store 204, theexample metadata database 206, the example dynamic range compressor 208,the example audio signal accessor 210, the example audio signalidentifier 212, the example metadata accessor 214, the example volumeadjuster 216, the example real time audio monitor 218, the example audiosignal outputter 220 and/or, more generally, the example media unit 106is/are hereby expressly defined to include a non-transitory computerreadable storage device or storage disk such as a memory, a digitalversatile disk (DVD), a compact disk (CD), a Blu-ray disk, etc.including the software and/or firmware. Further still, the example mediaunit 106 of FIG. 1 may include one or more elements, processes and/ordevices in addition to, or instead of, those illustrated in FIG. 2,and/or may include more than one of any or all of the illustratedelements, processes and devices.

Flowcharts representative of example machine readable instructions forimplementing the media unit 106 of FIGS. 1 and 2 are shown in FIGS. 3-5.In this example, the machine readable instructions comprise a programfor execution by a processor such as a processor 612 shown in theexample processor platform 600 discussed below in connection with FIG.6. The program may be embodied in software stored on a non-transitorycomputer readable storage medium such as a CD-ROM, a floppy disk, a harddrive, a DVD, a Blu-ray disk, or a memory associated with the processor612, but the entire program and/or parts thereof could alternatively beexecuted by a device other than the processor 612 and/or embodied infirmware or dedicated hardware. Further, although the example program isdescribed with reference to the flowcharts illustrated in FIGS. 3-5,many other methods of implementing the example media unit 106 mayalternatively be used. For example, the order of execution of the blocksmay be changed, and/or some of the blocks described may be changed,eliminated, or combined. Additionally or alternatively, any or all ofthe blocks may be implemented by one or more hardware circuits (e.g.,discrete and/or integrated analog and/or digital circuitry, a FieldProgrammable Gate Array (FPGA), an Application Specific Integratedcircuit (ASIC), a comparator, an operational-amplifier (op-amp), a logiccircuit, etc.) structured to perform the corresponding operation withoutexecuting software or firmware.

As mentioned above, the example processes of FIGS. 3-5 may beimplemented using coded instructions (e.g., computer and/or machinereadable instructions) stored on a non-transitory computer and/ormachine readable medium such as a hard disk drive, a flash memory, aread-only memory, a CD, a DVD, a cache, a random-access memory and/orany other storage device or storage disk in which information is storedfor any duration (e.g., for extended time periods, permanently, forbrief instances, for temporarily buffering, and/or for caching of theinformation). As used herein, the term non-transitory computer readablemedium is expressly defined to include any type of computer readablestorage device and/or storage disk and to exclude propagating signalsand to exclude transmission media. “Including” and “comprising” (and allforms and tenses thereof) are used herein to be open ended terms. Thus,whenever a claim lists anything following any form of “include” or“comprise” (e.g., comprises, includes, comprising, including, etc.), itis to be understood that additional elements, terms, etc. may be presentwithout falling outside the scope of the corresponding claim. As usedherein, when the phrase “at least” is used as the transition term in apreamble of a claim, it is open ended in the same manner as the term“comprising” and “including” are open ended.

Example machine readable instructions for implementing the media unit106 of FIGS. 1 and 2 and that may be executed to perform volumeadjustment of an audio signal are illustrated in FIG. 3. With referenceto the preceding figures and associated descriptions, the examplemachine readable instructions 300 begin with the example dynamic volumeadjuster 202 receiving an audio signal (Block 302). For example, theaudio signal accessor 210 may receive an audio signal from any mediasource or may access an audio signal from any location.

At block 304, the example dynamic volume adjuster 202 determines if themedia of the audio signal is identifiable. For example, the audio signalidentifier 212 may determine if the media of the audio signal isidentifiable. In some examples, the audio signal identifier 212 utilizesmedia identifiers (e.g., watermarks, ID3 tags, ISRC identifiers, etc.)embedded in the audio signal to compare to reference identifiers. Insome examples, the audio signal identifier 212 may interact with areference database located on the media unit 106 or located at adifferent location (e.g., a central facility). In such examples, theaudio signal identifier 212 may provide the identifier to the referencedatabase, where a search for a matching identifier may be performed. Insome examples, the audio signal identifier 212 utilizes fingerprintsderived from the audio signal to determine if the media represented inthe audio signal is identifiable. The audio signal identifier 212 mayutilize any technique to determine if media represented in the audiosignal is identifiable. In response to the media of the audio signalbeing identifiable, processing transfers to block 308. Conversely, inresponse to the media of the audio signal not being identifiable,processing transfers to block 306.

At block 306, the example media unit 106 dynamically compresses therange of the audio signal to alter the average volume level to satisfy athreshold related to a desired volume level. In some examples, thedynamic range compressor 208 dynamically compresses the audio signal inresponse to the media of the audio signal not being identifiable. Insome examples, the dynamic range compressor 208 compresses the audioincrementally such that the audio signal is compressed in areas where itdoes not satisfy the volume threshold. In some examples the dynamicrange compressor 208 compresses the overall audio signal such that theaverage volume of the audio signal satisfies the threshold related tothe desired volume.

At block 308, the example dynamic volume adjuster 202 obtains metadatafor the media including an average overall volume and a running volumeat a specified interval. For example, the example metadata accessor 214may retrieve metadata corresponding to the media identified by the audiosignal identifier 212 from a metadata database 206. In some examples,the example metadata accessor 214 receives data indicating an averageoverall volume for the media (e.g., an average volume for a track), aswell as running volumes (e.g., multiple volume values throughout themedia) at specified intervals (e.g., segments for which to calculate anaverage volume). In some examples, the metadata accessor 214 may accessmetadata including a value representing the difference between anaverage volume for the media and a desired volume. In such examples, themetadata may further include a gain value to be applied to the audiosignal to achieve the desired volume. In some examples, the metadataaccessor 214 may calculate any of these values (e.g., the averagevolume, the running volumes, the gain value, etc.) based on the metadatathat is obtained. In some examples, the metadata accessor 214 maycalculate the average volume for the media based on an average ofaverage volumes corresponding to segments of the media. For example, themetadata accessor 214 may access metadata corresponding to averagevolume data in specified increments throughout the media. In such anexample, the metadata accessor 214 may then calculate an average volumefor the media (e.g., for the track) by averaging the average values forall segments of the track.

At block 310, the example dynamic volume adjuster 202 applies an averagegain to the audio signal based on the metadata to adjust the averagevolume to satisfy a threshold related to the desired volume level. Insome examples, the example volume adjuster 216 applies the average gainto the audio signal to adjust the average volume of the audio signal tosatisfy a threshold related to the desired volume level. For example,the volume adjuster 216 may be configured with a desired volume level(e.g., negative twenty-one decibels loudness, K-weighted, relative tofull scale) and a specified threshold which some or all volume averagesmust satisfy. For example, the threshold may be a deviation from thedesired volume level or an acceptable range of volume levels. In someexamples, the volume adjuster 216 accesses the average gain valuedirectly from the metadata accessed by the metadata accessor 214. Insome examples, the volume adjuster 216 calculates the average gain valuebased on the metadata accessed by the metadata accessor 214. In someexamples, the volume adjuster 216 applies the average gain to the audiosignal overall. In some examples, the volume adjuster 216 utilizesmetadata pertaining to running volumes at specified intervals to applydifferent gain values to different segments of the media. The examplevolume adjuster 216 applies the average gain value as a way of adjustingthe volume to satisfy the volume threshold without influencing theoverall dynamics of the media.

At block 312, the example media unit 106 outputs the audio signal. Insome examples, the example dynamic volume adjuster 202 outputs the audiosignal. Detailed instructions to output the audio signal are provided inFIG. 4.

Example machine readable instructions for implementing the media unit106 of FIGS. 1 and 2 and that may be executed to output the audio signaland provide real time volume adjustment of the audio signal areillustrated in FIG. 4. With reference to the preceding figures andassociated descriptions, the example machine readable instructions 400begin with the dynamic volume adjuster 202 outputting a sample of theaudio signal to be presented. For example, the audio signal outputter220 may output a sample of the audio signal to be output to an amplifieror output device. As used herein, the sample of the audio signal refersto a segment of the audio signal, as opposed to outputting the entireaudio signal for presentation.

At block 404, the example dynamic volume adjuster 202 collects real timevolume measurement data as the audio sample is output. For example, thereal time audio monitor 218 collects data on the volume of the outputaudio signal. In some examples, the data collection may have a samplesize (e.g., three seconds) over which to collect the volumemeasurements, as well as a sample frequency (e.g., every seven hundredand fifty milliseconds) referring to the frequency with which volumemeasurement data is collected. In some examples, the real time audiomonitor 218 collects the data prior to the actual presentation of theaudio signal to enable last minute corrections of the audio signalvolume. In other examples, the real time audio monitor 218 collects thedata as the audio signal is presented to enable corrections of the audiosignal for subsequent presentation.

At block 406, the example dynamic volume adjuster 202 generates anaverage volume level for a specified timespan of the played audiosignal. In some examples, the example real time audio monitor 218generates the average volume level for the specified timespan of theplayed audio signal. In some examples, the example real time audiomonitor 218 generates the average volume measurement pertaining to theoutput audio sample. In some examples, the specified timespan refers tothe same duration of the sample of the audio signal. In other examples,the specified timespan may be different than the duration of the sampleand may include multiple samples (e.g., a three second averagingtimespan whereas samples are one second long).

At block 408, the example dynamic volume adjuster 202 determines if thevolume measurement for the specified timespan corresponds to the volumedata for the specified timespan as indicated in the metadata. Forexample, the real time audio monitor 218 may compare the generatedaverage volume level with the metadata corresponding to the mediarepresented by the audio signal. The example real time audio monitor 218may determine if the volume measurement for the specified timespancorresponds to the volume data in the metadata by determining adifference between the average volumes and determining if the differencesatisfies a matching threshold. In some examples, the audio signal maynot be identified, and metadata may not be available for a comparison,resulting in the volume measurement not matching any volume dataindicated in the metadata. In response to the volume measurement for thespecified timespan not corresponding to the volume data for thespecified timespan as indicated in the metadata, processing transfer toblock 410. Conversely, in response to the volume measurement for thespecified timespan corresponding to the volume data for the specifiedtimespan as indicated in the metadata, processing transfers to block416. In some examples, the example real time audio monitor 218 mayadditionally compare the volume measurement for the specified timespanto metadata corresponding to upcoming segments of the audio signal todetermine if a volume change is anticipated. In such examples, theexample real time audio monitor 218 may provide such forecastinginformation from the metadata to the volume adjuster 216 to adjust thevolume gradually to account for upcoming changes of the volume and/ordynamic range of the audio signal.

At block 410, the example dynamic volume adjuster 202 determines if theaverage volume level for the specified timespan satisfies a volumethreshold related to the desired volume level. For example, the realtime audio monitor 218 may determine if the average volume level for thespecified timespan satisfies the volume threshold related to the desiredvolume level (e.g., negative twenty-one decibels loudness, K-weighted,relative to full scale). In response to the average volume level for thespecified timespan satisfying the volume threshold related to thedesired volume level, processing transfers to block 414. Conversely, inresponse to the average volume for the specified timespan not satisfyingthe volume threshold related to the desired volume level, processingtransfers to block 410.

At bock 412, the example dynamic volume adjuster 202 determines thedifference between the average measured volume and the desired volumelevel. For example, the real time audio monitor 218 may subtract thedesired volume level from the average volume level for the specifiedtimespan to determine the difference between the two values.

At block 414, the example dynamic volume adjuster 202 applies a gainvalue based on the difference to adjust the audio signal to the desiredvolume level. For example, the volume adjuster 216 may calculate a gainvalue to apply to the audio signal based on the difference between theaverage measured volume and the desired volume level to adjust the audiosignal to the desired volume level. In some examples, the volumeadjuster 216 may apply the gain value to the remainder of the audiosignal. In some examples the volume adjuster 216 may apply the gainvalue as long as the audio signal corresponds to the same media. In someexamples, the volume adjuster 216 may apply the gain value locally toaccount for differences in volume levels at different segments in theaudio signal.

At block 416, the example dynamic volume adjuster 202 determines if thecurrent audio signal, corresponding to either a recognizable mediapresentation or no recognizable media presentation, has been entirelyoutput. For example, the audio signal identifier 212 may determine ifthe current audio signal corresponding to either a recognizable mediapresentation or no recognizable media presentation data has beenentirely output based on the presence (or lack thereof) of mediaidentifiers in the audio signal. For example, the audio signalidentifier 212 may continually monitor the audio signal for mediaidentifiers. The example audio signal identifier 212 may then interpreta change in the media identifier, or a change in the presence of a mediaidentifier (e.g., going from not finding a media identifier to finding amedia identifier) as an indicator that the audio signal corresponding toa media presentation or no recognizable media presentation has beenentirely output. The example audio signal identifier 212 performs thisverification to check if a new audio signal is present which may requirea new gain value to be computed based on available metadata, or requiredynamic range compression to be performed if he media is unidentifiable.In response to the current audio signal corresponding to a recognizablemedia presentation or no recognizable media presentation having beenentirely output, processing returns to the instructions of FIG. 3 andconcludes. Conversely, in response to the current audio signalcorresponding to a recognizable media presentation nor no recognizablemedia presentation not having been entirely output, processing transfersto block 402.

Example machine readable instructions for implementing the media unit106 of FIGS. 1 and 2 and that may be executed to perform volumeadjustment to normalize volume between sources and between media areillustrated in FIG. 5. With reference to the preceding figures andassociated descriptions, the example machine readable instructions 500begin with the example media unit 106 accessing an audio signal (Block502). In some examples, the audio signal accessor 210 accesses an inputaudio signal.

At block 504, the example media unit 106 determines whether mediaconveyed in the audio signal is identifiable. In some examples, theaudio signal identifier 212 determines whether media conveyed by theaudio signal is identifiable. The audio signal identifier 212 maydetermine whether any watermarks, codes, and/or other identifiers areembedded in the audio signal. In some examples, the audio signalidentifier 212 determines a signature based on the audio signal anddetermines whether the signature is represented in a storage locationwith reference signatures. In response to the media conveyed in theaudio signal being identifiable, processing transfers to block 508.Conversely, in response to the media conveyed in the audio signal notbeing identifiable, processing transfers to block 506.

At block 506, the example media unit 106 compresses or expands thedynamic range of the audio signal to satisfy a volume threshold. In someexamples, the dynamic range compressor 208 compresses or expands thedynamic range of the audio signal to satisfy the volume threshold. Insome examples, the volume threshold is a range within which the volumeof the audio signal must fall. In some examples, the volume threshold isa maximum or minimum volume value.

At block 508, the example media unit 106 identifies media conveyed inthe audio signal. In some examples, the audio signal identifier 212utilizes watermarks, codes, signatures, fingerprints, and/or any otheridentification techniques to identify the media conveyed in the audiosignal.

At block 510, the example media unit 106 obtains metadata including anaverage volume of the media and time varying volume measurements for themedia. In some examples, the metadata accessor 214 obtains the metadataincluding the average volume of the media and the time varying volumemeasurements for the media. The average volume for the media is acharacteristic volume of the media. Different songs, for example, mayhave different average volume values. The average volume value can thusbe utilized to help normalize volume levels between different media(e.g., different songs). The time varying volume measurements for themedia include instantaneous volume measurements for the media atspecific times. The time varying volume measurements can thus beutilized to compare an instantaneous volume of the input audio signalwith the expected values represented in the metadata, enablingnormalization of volume levels between different sources.

At block 512, the example media unit 106 computes a first gain valuebased on an average volume of the media to normalize the volume betweendifferent media. In some examples, the volume adjuster 216 computes thefirst gain value based on the average volume of the media to normalizethe volume between different media. To compute the first gain value, thevolume adjuster 216 computes the first gain value based on metadata fromthe metadata accessor 214 and a volume measured by the real time audiomonitor 218. The first gain value represents a gain that accounts forthe specific volume of the identified media. For example, a relativelyquiet song may have a larger positive gain than a relatively loudersong, in order to bring both songs to within a volume threshold range.

At block 514, the example media unit 106 computes a second gain valuebased on a comparison of the volume of the audio signal with timevarying volume measurements to normalize between sources. In someexamples, the example volume adjuster 216 computes a second gain valuebased on a comparison of the volume of the audio signal with timevarying volume measurements to normalize between sources. For example, amedia player connected to the media unit 106 via auxiliary input mayhave a different baseline volume than a CD. Thus, to normalize volumebetween different sources, an instantaneous comparison of the inputvolume with the time varying volume measurements of the metadata isperformed to determine a gain to offset source-specific volumedifferences. The volume level of the input signal prior to theapplication of the first gain (the gain pertaining to the average volumeof the media) is compared to the time-varying measurements for the mediain the metadata. In some examples, the time varying volume measurementsare not included in the metadata. In some such examples, the first gainvalue may be calculated and applied. Conversely, in some examples, theaverage volume measurement is not included in the metadata. In some suchexamples, the second gain value may be calculated and applied.

At block 516, the example media unit 106 calculates an applied gainvalue to apply to the audio signal based on the first gain value and thesecond gain value. In some examples, the volume adjuster 216 calculatesthe applied gain value to apply to the audio signal based on the firstgain value and the second gain value. In some examples, the applied gainvalue may be based on only the first gain value or only the second gainvalue.

At block 518, the example media unit 106 applies the applied gain valueto the audio signal. In some examples, the volume adjuster 216 appliesthe applied gain value to the audio signal.

At block 520, the example media unit 106 determines whether a change inmedia has been detected. In some examples, the audio signal identifier212 determines whether a change in media has been detected based on adifferent identification of the media, or based on a loss ofidentification of the media (e.g., watermarks and/or other identifies nolonger detected). In response to a change in media being detected,processing transfers to block 508. Conversely, in response to a changein media not being detected, processing transfers to block 522.

At block 522, the example media unit 106 determines whether a change insource has been detected. In some examples, the audio signal accessor210 determines whether a change in source has been detected. In responseto a change in source being detected, processing transfers to block 514.Conversely, in response to a change in source not being detected,processing transfers to block 524.

At block 524, the example media unit 106 determines whether to continuemonitoring. In response to continuing monitoring, processing transfersto block 520. Conversely, in response to not continuing monitoring,processing terminates.

FIG. 6 is a block diagram of an example processor platform 600 capableof executing the instructions to implement the methods of FIGS. 3-5 toimplement the example media unit 106 of FIGS. 1 and 2. The processorplatform 600 can be, for example, a server, a personal computer, amobile device (e.g., a cell phone, a smart phone, a tablet such as aniPad™), a personal digital assistant (PDA), an Internet appliance, a DVDplayer, a CD player, a digital video recorder, a Blu-ray player, agaming console, a personal video recorder, a set top box, or any othertype of computing device.

The processor platform 600 of the illustrated example includes aprocessor 612. The processor 612 of the illustrated example is hardware.For example, the processor 612 can be implemented by one or moreintegrated circuits, logic circuits, microprocessors or controllers fromany desired family or manufacturer. The hardware processor may be asemiconductor based (e.g., silicon based) device. In this example, theprocessor 612 implements the example dynamic volume adjuster 202, theexample data store 204, the example metadata database 206, the exampledynamic range compressor 208, the example audio signal accessor 210, theexample audio signal identifier 212, the example metadata accessor 214,the example volume adjuster 216, the example real time audio monitor218, the example audio signal outputter 220 and/or, more generally, theexample media unit 106 of FIG. 1. The processor 612 of the illustratedexample includes a local memory 613 (e.g., a cache). The processor 612of the illustrated example is in communication with a main memoryincluding a volatile memory 614 and a non-volatile memory 616 via a bus618. The volatile memory 614 may be implemented by Synchronous DynamicRandom Access Memory (SDRAM), Dynamic Random Access Memory (DRAM),RAMBUS Dynamic Random Access Memory (RDRAM) and/or any other type ofrandom access memory device. The non-volatile memory 616 may beimplemented by flash memory and/or any other desired type of memorydevice. Access to the main memory 614, 616 is controlled by a memorycontroller.

The processor platform 600 of the illustrated example also includes aninterface circuit 620. The interface circuit 620 may be implemented byany type of interface standard, such as an Ethernet interface, auniversal serial bus (USB), and/or a peripheral component interconnect(PCI) express interface.

In the illustrated example, one or more input devices 622 are connectedto the interface circuit 620. The input device(s) 622 permit(s) a userto enter data and/or commands into the processor 612. The inputdevice(s) can be implemented by, for example, an audio sensor, amicrophone, a camera (still or video), a keyboard, a button, a mouse, atouchscreen, a track-pad, a trackball, an isopoint device, and/or avoice recognition system.

One or more output devices 624 are also connected to the interfacecircuit 620 of the illustrated example. The output devices 624 can beimplemented, for example, by display devices (e.g., a light emittingdiode (LED), an organic light emitting diode (OLED), a liquid crystaldisplay, a cathode ray tube display (CRT), a touchscreen, a tactileoutput device, a printer and/or speakers). The interface circuit 620 ofthe illustrated example, thus, typically includes a graphics drivercard, a graphics driver chip and/or a graphics driver processor.

The interface circuit 620 of the illustrated example also includes acommunication device such as a transmitter, a receiver, a transceiver, amodem and/or network interface card to facilitate exchange of data withexternal machines (e.g., computing devices of any kind) via a network626 (e.g., an Ethernet connection, a digital subscriber line (DSL), atelephone line, coaxial cable, a cellular telephone system, etc.).

The processor platform 600 of the illustrated example also includes oneor more mass storage devices 628 for storing software and/or data.Examples of such mass storage devices 628 include floppy disk drives,hard drive disks, compact disk drives, Blu-ray disk drives, redundantarray of independent disks (RAID) systems, and DVD drives.

The coded instructions 632 to implement the methods of FIGS. 3-5 may bestored in the mass storage device 628, in the volatile memory 614, inthe non-volatile memory 616, and/or on a removable non-transitorycomputer readable storage medium such as a CD or DVD.

From the foregoing, it will be appreciated that example methods,apparatus and articles of manufacture have been disclosed that adjustthe volume of media such that media with different initial volumecharacteristics can be played at approximately the same volume, withoutaltering the original dynamics of the media. While conventionalimplementations of volume equalization continually adjust the volume andconsequently cause perceptible changes to the audio signal, examplesdisclosed herein enable volume equalization using an adjustment by anaverage gain value based on metadata pertaining to the media.Additionally, examples disclosed herein describe techniques forreal-time monitoring to adjust the volume of tracks in case ofdifferences between the audio signal and the corresponding metadatamedia upon which the appropriate average gain was originally calculated.Such techniques are advantageous over conventional implementations sincethey are imperceptible to users and enable different media fromdifferent or similar sources to be played at substantially the samevolume for a seamless media presentation experience.

An example apparatus to adjust volume is disclosed. The exampleapparatus includes an audio signal identifier to identify mediarepresented in an audio signal, a metadata accessor to access metadataassociated with the media in response to identifying the media in theaudio signal and determine, based on the metadata, an average volume forthe media. The example apparatus includes a volume adjuster to adjust anoutput volume of the audio signal based on an average gain value, theaverage gain value determined based on the average volume for the media.

In some examples, the example apparatus includes a real time audiomonitor to determine a difference between an average measured volume ofa sample of the audio signal and a desired volume level for a specifiedtimespan, wherein the volume adjuster to adjust the volume of the audiosignal based on a second gain value, the second gain value based on thedifference.

In some examples, the average gain value is an initial volume adjustmentapplied to the audio signal and the second gain value is a subsequentvolume adjustment applied to the audio signal.

In some examples, the example apparatus includes a dynamic rangecompressor to compress the audio signal when the audio signal identifieris unable to identify media represented in the audio signal.

In some examples, the example apparatus includes including an audiosignal accessor to buffer the audio signal, the buffering to cause adelay in outputting the audio signal to provide time for identifying themedia, accessing the metadata, and determining the average volume.

In some examples, the average gain value is determined based on a safelistening volume range.

In some examples, the average gain value is determined based on ahistorical volume setting for a source type of the audio signal.

An example non-transitory computer readable storage medium is disclosedherein. The example non-transitory computer readable storage mediumcomprises instructions that, when executed, cause a processor to atleast identify media represented in an audio signal, access metadataassociated with the media in response to identify the media in the audiosignal, determine, based on the metadata, an average volume for themedia, and adjust an output volume of the audio signal based on anaverage gain value, the average gain value determined based on theaverage volume for the media.

In some examples, the computer readable instructions, when executed,further cause the processor to determine a difference between an averagemeasured volume of a sample of the audio signal and a desired volumelevel for a specified timespan, and adjust the volume of the audiosignal based on a second gain value, the second gain value based on thedifference.

In some examples, the average gain value is an initial volume adjustmentapplied to the audio signal and the second gain value is a subsequentvolume adjustment applied to the audio signal.

In some examples, the computer readable instructions, when executed,cause the processor to compress the audio signal when media representedin the audio signal is not identified.

In some examples, the computer readable instructions, when executed,cause the processor to buffer the audio signal, the buffering to cause adelay in outputting the audio signal to provide time for identifying themedia, accessing the metadata, and determining the average volume.

In some examples, the average gain value is determined based on a safelistening volume range.

In some examples, the average gain value is determined based on ahistorical volume setting for a source type of the audio signal.

An example method disclosed herein includes identifying mediarepresented in an audio signal, accessing metadata associated with themedia in response to identify the media in the audio signal determining,based on the metadata, an average volume for the media and adjusting anoutput volume of the audio signal based on an average gain value, theaverage gain value determined based on the average volume for the media.

In some examples, the method includes determining a difference betweenan average measured volume of a sample of the audio signal and a desiredvolume level for a specified timespan and adjusting the volume of theaudio signal based on a second gain value, the second gain value basedon the difference.

In some examples, the average gain value is an initial volume adjustmentapplied to the audio signal and the second gain value is a subsequentvolume adjustment applied to the audio signal.

In some examples, the method further includes compressing the audiosignal when the media represented in the audio signal is not identified.

In some examples, the method further includes buffering the audiosignal, the buffering to cause a delay in outputting the audio signal toprovide time for identifying the media, accessing the metadata, anddetermining the average volume.

In some examples, the average gain value is determined based on a safelistening volume range.

Although certain example methods, apparatus and articles of manufacturehave been disclosed herein, the scope of coverage of this patent is notlimited thereto. On the contrary, this patent covers all methods,apparatus and articles of manufacture fairly falling within the scope ofthe claims of this patent.

What is claimed is:
 1. An apparatus to adjust audio volume, theapparatus comprising: an audio signal identifying circuit to identifymedia represented in an audio signal; a metadata accessing circuit to:access metadata associated with the media in response to identifying themedia in the audio signal; and determine, based on the metadata, anaverage volume for the media; and a volume adjusting circuit to adjustan output volume of the audio signal based on a first gain value, thefirst gain value determined using: a second gain value determined basedon the average volume for the media to enable normalization of theoutput volume of the audio signal between other media; and a third gainvalue determined based on a comparison of the audio signal and aninstantaneous volume measurement represented in the metadata to enablenormalization of the output volume of the audio signal between sources.2. The apparatus of claim 1, further including a real time audiomonitoring circuit to determine a difference between an average measuredvolume of a sample of the audio signal and a desired volume level for aspecified timespan, wherein the volume adjusting circuit to adjust theoutput volume of the audio signal based on a fourth gain value, thefourth gain value based on the difference.
 3. The apparatus of claim 2,wherein the volume adjusting circuit is to determine a fifth gain value,wherein the fourth gain value is an initial volume adjustment applied tothe audio signal and the fifth gain value is a subsequent volumeadjustment applied to the audio signal.
 4. The apparatus of claim 1,further including a dynamic range compressor to compress the audiosignal when the audio signal identifier is unable to identify the mediarepresented in the audio signal.
 5. The apparatus of claim 1, furtherincluding an audio signal accessing circuit to buffer the audio signal,the buffering to cause a delay in outputting the audio signal to providetime for identifying the media, accessing the metadata, and determiningthe average volume.
 6. The apparatus of claim 1, wherein the first gainvalue is determined based on a safe listening volume range.
 7. Theapparatus of claim 1, wherein the first gain value is determined basedon a historical volume setting for a source type of the audio signal. 8.A non-transitory computer readable storage medium comprising computerreadable instructions that, when executed, cause a processor to atleast: identify media represented in an audio signal; access metadataassociated with the media in response to identifying the media in theaudio signal; determine, based on the metadata, an average volume forthe media; and adjust an output volume of the audio signal based on afirst gain value, the first gain value determined using: a second gainvalue determined based on the average volume for the media to enablenormalization of the output volume of the audio signal between othermedia; and a third gain value determined based on a comparison of theaudio signal and an instantaneous volume measurement represented in themetadata to enable normalization of the output volume of the audiosignal between sources.
 9. The non-transitory computer readable storagemedium of claim 8, wherein the computer readable instructions, whenexecuted, cause the processor to: determine a difference between anaverage measured volume of a sample of the audio signal and a desiredvolume level for a specified timespan; and adjust the volume of theaudio signal based on a fourth gain value, the fourth gain value basedon the difference.
 10. The non-transitory computer readable storagemedium of claim 9, wherein the computer readable instructions, whenexecuted, cause the processor to determine a fifth gain value, whereinthe fourth gain value is an initial volume adjustment applied to theaudio signal and the fifth gain value is a subsequent volume adjustmentapplied to the audio signal.
 11. The non-transitory computer readablestorage medium of claim 8, wherein the computer readable instructions,when executed, cause the processor to compress the audio signal when themedia represented in the audio signal is not identified.
 12. Thenon-transitory computer readable storage medium of claim 8, wherein thecomputer readable instructions, when executed, cause the processor tobuffer the audio signal, the buffering to cause a delay in outputtingthe audio signal to provide time for identifying the media, accessingthe metadata, and determining the average volume.
 13. The non-transitorycomputer readable storage medium of claim 8, wherein the first gainvalue is determined based on a safe listening volume range.
 14. Thenon-transitory computer readable storage medium of claim 8, wherein thefirst gain value is determined based on a historical volume setting fora source type of the audio signal.
 15. A method comprising: identifyingmedia represented in an audio signal; accessing metadata associated withthe media in response to identifying the media in the audio signal;determining, based on the metadata, an average volume for the media; andadjusting an output volume of the audio signal based on a first gainvalue, the first gain value determined using: a second gain valuedetermined based on the average volume for the media to enablenormalization of the output volume of the audio signal between othermedia; and a third gain value determined based on a comparison of theaudio signal and an instantaneous volume measurement represented in themetadata to enable normalization of the output volume of the audiosignal between sources.
 16. The method of claim 15, further including:determining a difference between an average measured volume of a sampleof the audio signal and a desired volume level for a specified timespan;and adjusting the volume of the audio signal based on a fourth gainvalue, the fourth gain value based on the difference.
 17. The method ofclaim 16, further including determining a fifth gain value, wherein thefourth gain value is an initial volume adjustment applied to the audiosignal and the fifth gain value is a subsequent volume adjustmentapplied to the audio signal.
 18. The method of claim 15, furtherincluding compressing the audio signal when the media represented in theaudio signal is not identified.
 19. The method of claim 15, furtherincluding buffering the audio signal, the buffering to cause a delay inoutputting the audio signal to provide time for identifying the media,accessing the metadata, and determining the average volume.
 20. Themethod of claim 15, wherein the first gain value is determined based ona safe listening volume range.